1. Field of the Invention
The invention relates to a power converting apparatus, and more particularly to an AC-to-DC power converting apparatus having a multiplier-divider circuit.
2. Description of the Related Art
FIG. 1 illustrates a conventional AC-to-DC power converting apparatus disclosed in U.S. Pat. No. 7,057,440. The conventional AC-to-DC power converting apparatus converts an AC input voltage supplied by an AC power source 10 to a DC output voltage (Vc1), and includes a full-bridge rectifier 11, a power factor correction (PFC) circuit 12, a driving circuit 13, a pulse width modulation (PWM) circuit 14, a voltage-to-current converter 15, a first voltage detection circuit 17, a second voltage detection circuit 18 and a multiplier-divider circuit 19. The PFC circuit 12 adjusts and outputs the DC output voltage (Vc1) based on a driving signal (VD) from the driving circuit 13. The multiplier-divider circuit 19 generates an output signal (Vo4) associated with the driving signal (VD) based on an input current (IAC), which is converted from an input voltage (VAC) by a resistor 16, an input signal (Vo2) from the first voltage detection circuit 17, and an input signal (Vo3) from the second voltage detection circuit 18.
With further reference to FIG. 2, the multiplier-divider circuit 19 includes a pulse generator 191, a first multiplier-divider 192 and a second multiplier-divider 193. The pulse generator 191 generates, based on the input signal (Vo2), a plurality of control signals (Vsaw, PLS, /PLS, CLR, SMP). The first multiplier-divider 192 generates a sampling signal (Vo5) based on the input signal (Vo3) from the second voltage detection circuit 18, on an input current (IR) and on the control signals (Vsaw, PLS, /PLS, CLR, SMP) from the pulse generator 191. The second multiplier-divider 193 generates the output signal (Vo4) based on the sampling signal (Vo5) from the first multiplier-divider 192, the input current (IAC), and the control signals (Vsaw, PLS, /PLS, CLR, SMP) from the pulse generator 191. Each of the first and second multiplier-dividers 192, 193 includes a switching unit 194, and an adjusting unit 197 that includes an operational amplifier 195 and a sample-and-holder 196.
In such a configuration, since the control signals (Vsaw, PLS, /PLS, CLR, SMP) are required for operation of each of the first and second multiplier-dividers 192, 193, the pulse generator 191 for generating the control signals (Vsaw, PLS, /PLS, CLR, SMP) has a relatively complicated structure, and operation of each of the first and second multiplier-dividers 192, 193 is relatively complicated as well. Therefore, the conventional AC-to-DC power converting apparatus has a relatively complicated configuration, and is operated in a relatively complicated control manner. In addition, for the first multiplier-divider 192, the sampling signal (Vo5) generated by the sample-and-holder 196 is associated with a response speed of the operational amplifier 195 and input and output signals respectively inputted to and outputted by the operational amplifier 195. In this case, when the response speed is too fast or when one of the input and output signals is out of a respective signal range, distortion of the sampling signal (Vo5) may occur, thereby resulting in distortion of the output signal (Vo4) generated by the second multiplier-divider 193.